Course Icon

Natural Science - Year II

Unit 54: Rutherford and Atomic Structure

Course Materials are always under revision! Weblecture content may change anytime prior to two weeks before scheduled chat session for content.

SO Icon

Science Weblecture for Unit 54

This Unit's Homework Page History Lecture Science Lecture Lab Parents' Notes

Science Lecture for Unit 54: The Bohr Atom

For Class


More Atom Basics

Read about the development of the empty atom concept and the Bohr atom. [2 moderate web pages.] Don't focus on the mathematics, but try to understand the key relationships involved: what physical entities are being described? For example, 1/2mv2 is kinetic energy.

  • Rutherford discovered that radioactivity decreases geometrically as time passes. How is a geometric progression different from an arithmetic progression?
  • How do we explain the very small deflection most alpha particles experience passing near the nucleus?
  • Why does direct deflection back from the foil disprove the "plum pudding" model?
  • What is a hyperbolic path? How does it differ from a parabolic path or a circular path?
  • Why was large angle scattering important in determining the size of the nucleus?
  • What did Rutherford originally think the α particle was made of?
  • Can an electron have an orbit of any radius when it is part of an atom? Why is this a problem for classical mechanics?
  • How is the kinetic energy of an electron related to frequency? What does this frequency measure?
  • What did Richard Whiddington's experiments with x-rays show about atoms?
  • What is Balmer's formula? What does it predict? What is "n" in the formula?
  • How are the radius and speed of the orbit of an electron proportional to "n"?

A more graphic treatment of the different parts of the atom is presented at the Trium Safety Group site, by Noel Griffin.
[7 really short web pages with graphics: read them all:

  • Atomic structure
  • The Nucleus and Electrons
  • Atomic Number
  • Atomic Mass
  • Electron Orbits
  • The size of the electron
  • Chemical symbols

  • Why is a fixed structure hard to describe for the atom?
  • How many types of atoms occur "naturally"? How are "unnatural" atoms produced?
  • Why is the mass of the electron usually ignored when determining the mass of an atom?
  • What is an electron shell?
  • What parts of the atom are affected by chemical reactions (such as the recombination of sugar molecules into carbon dioxide and water)?
  • Roughly how much larger than the nucleus is the atom with its electron shell?

Study/Discussion Questions

Further Study On your Own (Optional)